706 research outputs found
Low-momentum nucleon-nucleon interaction and shell-model calculations
We discuss the use of the low-momentum nucleon-nucleon NN interaction V-low-k
in the derivation of the shell-model effective interaction and emphasize its
practical value as an alternative to the Brueckner G-matrix method. We present
some selected results of our current study of exotic nuclei around closed
shells, which have been obtained starting from the CD-Bonn potential. We also
show some results of calculations performed with different phase-shift
equivalent NN potentials, and discuss the effect of changes in the cutoff
momentum which defines the V-low-k potential.Comment: 5 pages, 5 figures, 1 table, Talk presented at CDN05, 31 Jan - 4 Feb
2005, University of Tokyo, Japa
Fully microscopic shell-model calculations with realistic effective hamiltonians
The advent of nucleon-nucleon potentials derived from chiral perturbation
theory, as well as the so-called V-low-k approach to the renormalization of the
strong short-range repulsion contained in the potentials, have brought renewed
interest in realistic shell-model calculations. Here we focus on calculations
where a fully microscopic approach is adopted. No phenomenological input is
needed in these calculations, because single-particle energies, matrix elements
of the two-body interaction, and matrix elements of the electromagnetic
multipole operators are derived theoretically. This has been done within the
framework of the time-dependent degenerate linked-diagram perturbation theory.
We present results for some nuclei in different mass regions. These evidence
the ability of realistic effective hamiltonians to provide an accurate
description of nuclear structure properties.Comment: 6 pages, 9 figures, talk presented at INPC2010, Vancouver, July 4 -9
2010. Accepted for publication in Journal of Physics: Conference Serie
Pairing and realistic shell-model interactions
This paper starts with a brief historical overview of pairing in nuclei,
which fulfills the purpose of properly framing the main subject. This concerns
the pairing properties of a realistic shell-model effective interaction which
has proved very successful in describing nuclei around doubly magic 132Sn. We
focus attention on the two nuclei 134Te and 134Sn with two valence protons and
neutrons, respectively. Our study brings out the key role of one particle-one
hole excitations in producing a significant difference between proton and
neutron pairing in this region
Nuclear Structure Calculations and Modern Nucleon-Nucleon Potentials
We study ground-state properties of the doubly magic nuclei 4He, 16O, and
40Ca employing the Goldstone expansion and using as input four different
high-quality nucleon-nucleon (NN) potentials. The short-range repulsion of
these potentials is renormalized by constructing a smooth low-momentum
potential V-low-k. This is used directly in a Hartree-Fock approach and
corrections up to third order in the Goldstone expansion are evaluated.
Comparison of the results shows that they are only slightly dependent on the
choice of the NN potential.Comment: 5 pages, submitted to Physical Review
Shell-model study of the N=82 isotonic chain with a realistic effective hamiltonian
We have performed shell-model calculations for the even- and odd-mass N=82
isotones, focusing attention on low-energy states. The single-particle energies
and effective two-body interaction have been both determined within the
framework of the time-dependent degenerate linked-diagram perturbation theory,
starting from a low-momentum interaction derived from the CD-Bonn
nucleon-nucleon potential. In this way, no phenomenological input enters our
effective Hamiltonian, whose reliability is evidenced by the good agreement
between theory and experiment.Comment: 7 pages, 11 figures, 3 tables, to be published in Physical Review
Proton-Neutron Interaction near Closed Shells
Odd-odd nuclei around double shell closures are a direct source of
information on the proton-neutron interaction between valence nucleons. We have
performed shell-model calculations for doubly odd nuclei close to Pb,
Sn and Sn using realistic effective interactions derived from
the CD-Bonn nucleon-nucleon potential. The calculated results are compared with
the available experimental data, attention being focused on particle-hole and
particle-particle multiplets. While a good agreement is obtained for all the
nuclei considered, a detailed analysis of the matrix elements of the effective
interaction shows that a stronger core-polarization contribution seems to be
needed in the particle-particle case.Comment: 8 pages, 6 figures, Proccedings of the International Conference
"Nuclear Structure and Related Topics", Dubna, Russia, September 2-6, 2003,
to be published in Yadernaia Fizika (Physics of Atomic Nuclei
Nuclear Structure Calculations with Low-Momentum Potentials in a Model Space Truncation Approach
We have calculated the ground-state energy of the doubly magic nuclei 4He,
16O and 40Ca within the framework of the Goldstone expansion starting from
various modern nucleon-nucleon potentials. The short-range repulsion of these
potentials has been renormalized by constructing a low-momentum potential
V-low-k. We have studied the connection between the cutoff momemtum Lambda and
the size of the harmonic oscillator space employed in the calculations. We have
found a fast convergence of the results with a limited number of oscillator
quanta.Comment: 6 pages, 8 figures, to be published on Physical Review
Shell-model studies on exotic nuclei around 132Sn
The study of exotic nuclei around 132Sn is a subject of current experimental
and theoretical interest. Experimental information for nuclei in the vicinity
of 132Sn, which have been long inaccessible to spectroscopic studies, is now
available thanks to new advanced facilities and techniques. The experimental
data which have been now become available for these neutron-rich nuclei may
suggest a modification in the shell structure. They are, in fact, somewhat
different from what one might expect by extrapolating the existing results for
N<82, and as a possible explanation a change in the single-proton level scheme
has been suggested. The latter would be caused by a more diffuse nuclear
surface, and could be seen as a precursor of major effects which should show up
at larger neutron excess. New data offer therefore the opportunity to test the
shell model and look for a possible evolution of shell structure when going
toward neutron drip line. This is stimulating shell-model studies in this
region. Here, we present an overview of recent shell-model studies of 132Sn
neighbors, focusing attention on those calculations employing realistic
effective interactions.Comment: 8 pages, 4 tables, invited talk at INPC2007, Tokyo, Japan, June 3-8
2007. To be published in Nuclear Physics
Shell-model study of quadrupole collectivity in light tin isotopes
A realistic shell-model study is performed for neutron-deficient tin isotopes
up to mass A=108. All shell-model ingredients, namely two-body matrix elements,
single-particle energies, and effective charges for electric quadrupole
transition operators, have been calculated by way of the many-body perturbation
theory, starting from a low-momentum interaction derived from the
high-precision CD-Bonn free nucleon-nucleon potential. The focus has been put
on the enhanced quadrupole collectivity of these nuclei, which is testified by
the observed large B(E2;0+ -> 2+)s. Our results evidence the crucial role
played by the Z=50 cross-shell excitations that need to be taken into account
explicitly to obtain a satisfactory theoretical description of light tin
isotopes. We find also that a relevant contribution comes from the calculated
neutron effective charges, whose magnitudes exceed the standard empirical
values. An original double-step procedure has been introduced to reduce
effectively the model space in order to overcome the computational problem.Comment: 6 pages, 6 figures, 2 table
p-Shell Nuclei and Two-Frequency Shell Model with a Realistic Effective Interaction
We have studied p-shell nuclei using a two-frequency shell-model approach
with an effective interaction derived from the Bonn-A nucleon-nucleon potential
by means of a G-matrix folded-diagram method. First, we briefly describe our
derivation of the effective interaction in a model space composed of harmonic
hoscillator wave functions with two different length parameters, b_in and
b_out, for the core and the valence orbits, respectively. Then we present some
selected results of our calculations. We show that a good agreement with
experiment is obtained, which is definitely better than that provided by a
standard one-frequency calculation. A comparison with results obtained from
large-basis shell-model calculations is also made.Comment: 9 pages, 1 figure, talk presented at VIII Convegno di Fisica Nucleare
Teorica, Cortona, 18-21 Ottobre 200
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